header{
    background-color: #333;
    color: #fff;
    display: flex;
    height: 105px;
    font-size: 30px;
}
ul{
    display: flex;
    list-style: none;
}
ul li:hover{
    height: 45px;
    background-color: black;
}
ul a{
    color: #fff;
    text-decoration: none;
    margin-left: 15px;
    margin-right: 15px;
    transition: color 0.3s;
}
ul a:hover{
    color: #fff;
}